The ISO base media file format (ISOBMFF) specifies a generic structure for the storage and transport of timed media such as audio, video, and teletext. Recently, work has been initiated towards extending ISOBMFF's capabilities to enable the handling of still images and image sequences also. To enable storage and transport of image sequences, the Image File Format has been defined in ISO/IEC 23008-12 also known as MPEG-H Part 12, the definition being based on the ISO base media file format.
Among other properties, the Image File Format supports derived images. An item is a derived image, when it includes a ‘dimg’ item reference to another item. A derived image is obtained by performing a specified operation, such as rotation, to specified input images. The operation performed to obtain the derived image is identified by the item_type of the item. The image items used as input to a derived image may be coded images or they may be other derived image items.
A Multipurpose Internet Mail Extension (MIME) is an extension to an email protocol which makes it possible to transmit and receive different kinds of data files on the Internet, for example video and audio, images, software, etc. An internet media type is an identifier used on the Internet to indicate the type of data that a file contains. Such internet media types may also be called as content types. Several MIME type/subtype combinations exist that can contain different media formats. Content type information may be included by a transmitting entity in a MIME header at the beginning of a media transmission. A receiving entity thus may need to examine the details of such media content to determine if the specific elements can be rendered given an available set of codecs. In the absence of the parameters described here, it is necessary to examine each media element in order to determine the codecs or other features required to render the content.
The Image File Format specifies two MIME types, one for images and image collections, and another one for image sequences. The format of the codecs parameter is specified for these MIME types. However, the specification lacks the consideration for derived images, which may lead to various problems, such as the player consuming time for assessing if it is capable of composing the derived image before performing the operations.